Rinse shrimp, calamari, scallops, mussels and fish under cold water. Pat dry with paper towels. Trim any tough parts from calamari and halve larger scallops. Keep seafood chilled until ready to add to the soup.

Discard any mussels that remain open after a light tap. Keep mussels in the refrigerator in a bowl covered with a damp towel until use.

Make Broth & Vegetables

Heat a large heavy-bottomed pot or Dutch oven over medium heat. Add 2 tbs extra-virgin olive oil. When shimmering, add the diced onion, sliced fennel and diced carrot. Cook, stirring occasionally, until vegetables are softened and translucent, about 6–8 minutes.

Add the minced garlic and 1 tbs tomato paste. Cook 1 minute until fragrant, stirring to combine and brown the tomato paste lightly.

Pour in 120 ml dry white wine to deglaze the pot, scraping any browned bits from the bottom. Let the wine reduce by about half, roughly 2–3 minutes.

Stir in the 14 oz crushed tomatoes, 700 ml fish or chicken stock, 1 bay leaf, 2 thyme sprigs and 1 tsp crushed red pepper flakes. Add 1 tsp sugar if the tomatoes taste very acidic. Bring the mixture to a gentle simmer.

Reduce heat to maintain a low simmer and cook uncovered for 15 minutes to marry flavors. Taste and season with about 1 tsp sea salt and 1/2 tsp freshly ground black pepper, adjusting to preference.

Add Seafood & Greens

Increase heat so the broth returns to a gentle simmer (not a boil). Add the fish chunks first and simmer 2 minutes — fish is delicate and will start to firm immediately.

Add the scallops and calamari rings. Simmer for 1–2 minutes.

Add the shrimp and mussels. Cover the pot and simmer 3–4 minutes, or until shrimp are pink and opaque, scallops are firm, calamari is tender, and mussels have opened. Discard any mussels that remain closed.

Stir in the packed 4 cups fresh baby spinach and cook 1 minute, just until wilted.

Remove and discard the bay leaf and thyme stems. Squeeze the juice of 1 lemon into the soup, stir in 1 tsp olive oil, and taste for final seasoning, adding more salt/pepper or a pinch more red pepper flakes if desired.

Finish & Serve

Ladle the soup into warmed bowls, dividing the seafood evenly. Sprinkle chopped fennel fronds and 2 tbs chopped parsley over each bowl as garnish.

Serve immediately with crusty bread or garlic crostini. Offer grated parmesan at the table if desired (note: parmesan is optional and not traditional with seafood, but some guests like it).